Each monthly issue of the Henry Shaw Cactus Digest includes club updates, columns and articles by members on their favorite aspects of cactus and succulent culture. Follow the link below this item to read select Digest articles -- or join HSCS to receive every article in the print version of the Digest.

Ant PlantsBy Bob Harris

When you hear the words "ant plant," you know exactly what the plant is, don't you? Sure, we see them in the HSCS cactus show annually.

A University of Connecticut website answered a Google online search request with a long listing of "ant plants," which included:

All the above plants have symbiotic relationships with ants. Some of these plants are caudiciforms -- another not on the list is Macleania insignis, in the Ericaceae family. An excellent website for detailed information about their symbiotic relationships can be found at http://www.duke.edu/nplummer/intro.html.

Hydnophytums and myrmecodias are found from Thialand to Fiji. Their stems enlarge into a tuber with chambers inside. The chambers have entrance holes which allows ants access. Nutrients released by decay of the ants' waste (mostly leftover insect pieces) are absorbed by special "warts" inside the chambers.

Myrmecodia species have separate smooth-walled chambers that ants inhabit and warty chambers that serve as debris dumps. In hydnophytums, the chambers are less specialized, and the warts tend to be concentrated toward the ends of the chambers.

So the ants provide nutrition and the plant provides shelter. Even though the plants have a caudex or tuber, they are not necessarily succulents. Their culture and indigenous area do not seem to reflect succulents.

The acacias provide shelter inside their thorns, and the ants in return protect the plants from browsing animals and bugs, which might eat their leaves. Some even clear the area around the trunks of plants, eliminating growing competition.

Some of these plants could be considered succulents or at least caudex plants. It is easy to see why the botanical names are important when ordering or identifying plants.

Missouri Botanical Garden has an exhibit of ant plants in the Climatron. It is located along the outside railing near the location of the old cactus house. There is also an acacia and ant exhibit in the educational section of the Climatron.